Wednesday, June 18, 2014

New paper predicts fewer cyclones in the Indian Ocean if the climate warms

A new paper published in the International Journal of Climatology predicts warming will decrease the number of cyclones in the Bay of Bengal, Indian Ocean. According to the authors,

"The model's simulated frequency of storms is an overestimation of observations although the frequency of model's simulated storms during 2071–2100 is less than that of during 1961–1990."

In other words, the model overpredicted the number of historical cyclones from 1961-1990 and thus future predictions may be exaggerated, but nonetheless the same model predicts fewer storms from 2071-2100 than the period 1961-1990.

Global warming decreases the temperature gradient between the equator and poles, and temperature gradients, not absolute temperatures, drive all extreme weather including cyclones and hurricanes. Therefore, a warmer world is expected to have fewer cyclones, hurricanes, and extreme weather, not more.

The paper joins many others predicting fewer cyclones, hurricanes, and storms in a warmer climate.

The aim of this paper is to study the model's simulated frequency, track, intensity and location of cyclonic storms (CSs) and severe cyclonic storms (SCSs) in the Bay of Bengal (BoB), India. For the purpose, the PRECIS (Providing REgional Climates for Impacts Studies) a regional climate modelling system, of UK Met Office, is used. This model is integrated for the period 1961–1990 (baseline) and the future time period 2071–2100 (High emission scenario, A2). To run the model, the initial and lateral boundary conditions are supplied by UK Met Office. The analysis of frequency, track, intensity and location are carried out for May, June, September and October for the period 1961–1990 and 2071–2100. To evaluate the model's performance in simulating storms frequency during 1961–1990, chi square test is carried out with observed storms for the same period. The model's simulated frequency of storms is an overestimation of observations although the frequency of model's simulated storms during 2071–2100 is less than that of during 1961–1990. In general, model's simulated storms are found moving in the northwest direction from their initial location in all months during 1961–1990 and 2071–2100. In model's simulations, the drop in central pressure is relatively more in the months of May, June, September and October during 2071–2100 compared with that during 1961–1990. During 2071–2100, more intense storms may be possible in the months of May and June compared with that of September and October. It is observed that the model is able to simulate the initial locations of storms during 1961–1990 and 2071–2100 close to observations for the months of June and September, especially.